There is always a way. Send them a personal message and attach a .doc file with the requirement for an email address and tell them to use the same trick. You could also use software called 'Privnote'. Those are the messages that gets deleted after one view so there is no way Fiverr could know what was in the message after your customer reads it.
Guys, Thanks for reply. My Fiverr account has been blocked. there I got some regular clients. I have completed some orders but couldn't deliver those, because I can no longer login to my account. Now clients are asking me "what's the problem?". I get notification in my email from fiverr but I can't reply them. Can anyone help me to contact them through their email id that were used to register in Fiverr? Or is there any other way!
Perhaps you have a friend on Fiverr with an active account who can contact these folks and let them know what is going on, give them your email address, etc.?